1. Field of the Invention
The invention relates to a zoom lens used in an extremely small imaging module, and in particular, to an electronic imaging apparatus in which an imaging module is considered to achieve compactness of a zoom lens.
2. Description of Related Art
In recent years, digital cameras have been popularized as the next generation cameras of an alternative to silver halide film cameras. More recently, the digital cameras have become increasingly compact and slim. Even in mobile phones being popularized at the same time, camera functions are retained (which are hereinafter referred to as imaging modules). To mount the imaging modules in the mobile phones, however, they must be made smaller and slimmer than the digital cameras. However, zoom lenses so downsized that they can be mounted in the mobile phones are little known nowadays.
In order to satisfy very severe size conditions of compact and slim design, it is necessary to consider Means A-D described below.    A. A collapsible mount type of lens barrel is used to incorporate an optical system along the direction of the thickness (depth) of a camera body. This collapsible mount type of lens barrel is such that the optical system is shifted out of the camera body on photographing and is incorporated in the camera body on carrying.    B. A bending optical system is adopted to incorporate the optical system along the direction of the width or height of the camera body. This bending optical system is constructed so that the optical path (optical axis) of the optical system is bent by a reflecting optical element, such as a mirror or prism.    C. The optical system is incorporated along the direction of the width of the camera body (for example, in the hinge portion of the mobile phone), without changing the length of the optical system.    D. The optical system is mounted in connection with the camera body, with the length of the optical system kept to a predetermined value, so that a connecting portion can be rotated. By doing so, it is only necessary that even when the length of the optical system in a longitudinal direction is greater than the thickness of the camera body on photographing, the longitudinal direction of the optical system is made to coincide with the direction of the width of the camera body on incorporating. Thus, in an incorporated state, the thickness of the camera body is not increased.
In the compact and slim design, it is particularly desired that the optical system can be incorporated along the direction of the thickness of the camera body as in Means A and B. Conventional examples using Means A and B are set forth, for example, in Japanese Patent Kokai Nos. 2002-365543 and 2003-43354, respectively.